Antiplumming agents for photographic emulsions



Patented Feb. 15, 1949 ANTIPLUMMING AGENTS FOR PHOTO- GRAPHIC EMULSIONS Edward B. Knott and John Morgan, Wealdstone,

England, assignors to Eastman Kodak Company, Rochester, N. Y., a corporation of New Jersey No Drawing. Application June 19, 1947, Serial No. 755,718. In Great Britain June 20, 1946 8 Claims.

This invention relates to anti-plumming agents for photographic materials and to a method of preventing plumming and bronzing of the developed images given by photographic silver halide emulsion, especially emulsions in which the halide is partly or wholly chloride.

The development of exposed silver halide photographic emulsions leads to the formation of silver images which may vary considerably in colour depending on the size of the silver halide grain and on the type of developer used. Generally the finer the developed grain the greater is the tendency for the image to appear brown or green-brown in colour but in many cases it is desirable that the image should be a neutral grey or black or blue-black.

A similar disadvantage which is often experienced is the liability of the developed image to the effect known as pl-rimming or bronzing which occurs during the hot-glazing of prints and manifests itself in a deterioration of the image colour and of the density.

It is, accordingly, an object of our invention to provide photographic materials containing antiplumming agents. A further object is to provide a method of preventng plumming and bronzing during the hot-glazing of photographic prints. Other objects will become apparent hereinafter.

In accordance with our invention we provide a photographic material having a layer containing as an anti-plumming agent a compound represented by the formula:

where R represents an alkyl group and X represents a halogen atom. Our invention also provides a method of preventing plumming and bronzing during the hot-glazing of photographic prints which comprises developing a gelatinosilver halide emulsion'on which the prints are made in the presence of the compound represented by the above-mentioned formula.

Although in the said formula R is defined as representing an alkyl group it is to be understood that for the purpose of this specification and the appended claims where the term alkyl is used it includes substituted alkyl.

Compounds which are particularly effective are those in which R represents an amide-substituted alkyl group, i.e., an alkyl group containing the groups NH2.CO-, whilst those in which the nitrogen atom of the said amido group carries a nitrogen-containing heterocyclic residue are preferred; for example, compounds of the type which are specially advantageous are those represented by the formula:

wherein X again represents a halogen atom and Y represents a member selected from the group consisting of pyriclyl, quinolyl, thiazyl, benzthiazyl, pyrimidyl, etc.

The compounds of our invention are added, preferably to the emulsion layer or layers but they are also effective, when of the requisite solubility, if added to the developing or processing solutions or to other layers carried on the sensitive emulsion support such as the backing layer or supercoat. Alternatively, the sensitive layer may be bathed in a solution of the agent before or after exposure. The substance is added to the emulsion layer in amounts corresponding to 0.1 to 6.0 g., but preferably about 0.5 to 1.5 g./litre of finished emulsion, or to a developer or fixing bath at the rate of 0.2 to 4.0 g. per litre, preferably about 1 g. per litre. When the layer is simply bathed in a solution of the. compound this may contain up to 5% of the compound in Water.

The compounds are very effective as antipluinming agents when used in any of the Ways previously described or by bathing the image in the solution of the compound after fixation.

They are also useful, when added to the developer, for producing blue-black images and for preventing or reducing the overall silver deposit termed fog Which is frequently obtained on developing silver halide emulsions.

Although in this specification we have described our invention mainly with reference to the use of our new agents in developing solutions and anti-plumming baths it should be understood that the invention is by no means limited to such baths. Thus, although the agent is preferably added to the developing solutions (when not already present in the photographic material) it may be added in the fixing bath or at any stage prior to Washing since sufficient of the compound will be adsorbed to the silver grains to give the desired anti-plumming effect during hot-glazing of the print. 1

The invention is illustrated by the following examples of compounds which may be used,

together with their methods of preparation and use:

from alcohol-ether, forming flat, fatty needles, M.P. 97 0.

Example 4.-S-amidoethylthiuronium chloride Finely powdered thiourea (15.2 g.), chloracet amide- (18.7 g.) and ethyl alcohol (190 0.0.) were refluxed for 2 hours. The salt which separated during. this time-was-collected hot, washed with alcohol and ether and dried. From water it formed colourless needles, M.P. 222 C. (decomp).

Example 5.S-2-thiazylamidomethylthiuronium chloride Z-chloracetamidothiazole was obtained by chloracetylating 2-aminothiazole in pyridine, and precipitating the amide with acetic acid. This product (2.3g),powderedthiourea (1.3 g.) and ethyl alcohol (40 0.0.) were refluxed for 2 hours. Crystallization commenced after 5 mins. It was collected, washed with alcohol and recrystallized from. a little water forming fawn needles, M.P. 231 C. (decomp.).

Example 6.-S'-2-pyridylamidomethylthiuroniam chloride NHzCl 2-chloracetamidopyridine was obtained by treating 2-aminopyridine with chloracetyl chloride in pyridine and precipitating with dilute acetic acid. This product (2.3 g.), thiourea (1.1 g.) and ethyl alcohol cc.) were refluxed for 2 hours. The crystals which had separated were collected, washed with alcohol, and. recrystallized from a little water. forming fawn. needles, M.P. 225 C. (decomp).

EXAMPLES or Usr:

Example A 1 g. of S-ethylthiuronium bromide added to 1 litre of a silver chloride emulsion (containing approx. 20 g. AgCl per litre) gave an image of slightly bluer tone when the emulsion was coated on paper, exposed, and developed in a normal metol-hydroquinone developer. The maximum density obtainable was slightly increased, and did not decrease on hot glazing, unlike that of the untreated emulsion.

Example B The 1 g. of S-ethylthiuronium bromide used in Example A above was replaced by 1 g. of each of the compounds described in Examples 2, 3 or 4 and similar. results obtained.

Example C Replacement of S-ethylthiuronium bromide in Example A by the compound described in Example 5 or 6 gave a still bluer image and higher maximum density, with no loss on hot glazing.

Example D 1 g. of the compound described in Example 6 added to 1 litre of a silver chlorobromide emulsion changed the normal warm brown tone of the blacks to neutral, On development in a normal metol-hydroquinone developer. There was also a large increase in maximum density, and no plumming on glazing, although this emulsion lost density badly on glazing when untreated. Addition of as little as 0.2 g./litre of the compound of Example 6 was suficient to stop this plumming.

Example E (a) A silver ohloro-bromide emulsion coated on paper was exposed to a step wedge, developed and fixed.

(b) The same paper was treated as in (a), but with the addition of 1 g. of the compound described in Example 5 to 1 litre of developer.

(0) The same paper was treated as in (a), but with the addition of 5 g. of the same compound to 1 litre of fixer.

(d) The same paper treated as in (a), but after fixation, was bathed in a solution of 5 g. of the same compound in cc. water for 5 minutes. On hot glazing the paper treated according to processes (b), (c) or (dlgave very deep blacks, while that processed according to (a) showed a big loss in density.

Having thus described our invention, what we claim is:

1. A gelatino-silver halide emulsion contain ng as an anti-plumming agent a compound represented by the formula:

wherein R represents an alkyl group and X rep-- resents a halogen atom.

2. A gelatino-silver halide emulsion containing as an anti-plumming agent a compound represented by the formula:

whereinR represents. an, amido-substituted'. alkyl group and)! represents. a halogenatom.

3. A gelatino-silver halide emulsion wherein the halide is at least partly chloride, containing as an anti-plumming agent a compound represented by the formula:

NHrX

YNH-O o-c m-s-O NH: wherein Y represents a nitrogen-containing heterocyclic residue and X represents a halogen atom.

4. A gelatino-silver halide emulsion wherein the halide is at least partly chloride, containing as an anti-plumming agent a compound represented by the formula:

wherein R represents an alkyl group and X represents a halogen atom.

6. The method of preventing plumming and bronzing during the hot-glazing of photographic prints, which comprises developing a gelatinosilver halide emulsion on which the prints are made, in the presence of a compound having the formula:

6 wherein R represents an amido-substituted alkyl group and X represents a halogen atom.

7. The method of preventing plumming and bronzing during the hot-glazing of photographic prints, which comprises developing a gelatinosilver halide emulsion on which the prints are made, the halide of said emulsion being at least partly chloride, in the presence of a compound having the formula:

\ Y-NH-C O-0H1S0 NHa wherein Y represents a nitrogen-containing heterocyclic residue and X represents a halogen atom. i 8. The method of preventing plumming and bronzing during the hot-glazing of photographic prints, which comprises developing a gelatinosilver halide emulsion on which the prints are made, the halide of said emulsion being at least partly chloride, in the presence of a compound having the formula:

NHzX

YNHC OCH2SC wherein Y represents a member selcted from the group consisting of a pyridyl group, a quinolyl group, a thiazyl group, a benzthiazyl group and a pyrimidyl group and X represents a halogen atom.

EDWARD B. KNOTT. ,JOHN MORGAN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,124,159 Weyde July 19, 1938 2,255,731 Ham et al Sept. 9, 1941 

